The sutureless excimer laser assisted non-occlusive anastomosis (SELANA); a feasibility study in a pressurized cadaver model

We operated on four pressurized cadaveric heads at the ‘Yaşargil Microneurosurgery Laboratory’ of the department of neurosurgery at the University of Arkansas for Medical Sciences, Little Rock.

The cadaver model preparation was performed similar to methods previously described. [1] In short, after decapitation of a formalin fixed cadaver at approximately C6/C7, the common carotid arteries (CA) and vertebral arteries (VA) were exposed and cannulated. In addition, an 8-10-gage tube was intradurally inserted left and right from the spinal canal and advanced to reach the intracranial subarachnoid space. Subsequently, the canal was plugged with bone wax. Tap water was used to repeatedly irrigate and flush the vessels and the subarachnoid space to remove clots, tissue debris, and formalin fixative. Leaks from arteries or veins on the sectioned surface of the neck were sealed either using ligation or coagulation. Subsequently, artificial blood was made with a mixture of red poster paint and water. Serum bags with artificial blood were attached to the CA’s and VA’s. Pressure bags were put over the serum bags. The arterial pressure bags were connected to a balloon pump (Datascope® 90 T) providing pulsating pressure. We selected a rate of 60 pulses per minute, a baseline pressure of 80 mm Hg and a ‘systolic’ peak pressure of 110 mmHg.

On each of the four cadaver heads, a bilateral combined pterional/pretemporal/transcavernous approach was performed as earlier described. [2, 3, 5, 11] In short, a standard pterional skin incision was made that extended below the zygoma, just anterior to the tragus. The skin flap was separated from the temporal fascia down to the fat pad over the zygoma. The temporal muscle was cut anteriorly and superiorly and was retracted inferiorly. The bone flap included the anterior temporal squama, and extended down to the temporal floor anteriorly. The pterion and the sphenoidal wings were drilled to expose the dura over the anterior temporal pole. The dura was cut parallel to the sylvian fissure, the medial cisterns were opened, the Sylvian fissure was opened laterally to medially and Liliequist’s membrane was opened. Subsequently, the anterior clinoid process was removed. The roof of the cavernous sinus was incised just medially to the third nerve. Since the venous system was not pressurized, no leak occurred. The incision was progressively enlarged posteriorly until the posterior clinoid process was encountered which was also removed. This exposure facilitated a good view on all arteries on which we planned an anastomosis, including the MCA after the bifurcation (M2), the proximal MCA (M1), the ICA bifurcation, the proximal ICA, the proximal ACA (A1), the PCA after the posterior communicating artery (P2) and the proximal PCA (P1/basilar artery; BA).

Before starting this study, application of ELANA and SELANA anastomoses was trained on the ELANA practice model [7] to minimize the influence of a learning curve. All anastomoses were made by the first author (TPCvD).

For all conventional ELANA anastomoses, we used thoracic rabbit aorta’s as bypass graft. These were harvested in a consumption slaughterhouse from rabbits of 3-4 kg. All side branches were occluded with microsutures.

To make a conventional ELANA anastomosis (Fig. 1a), we first attached a 2.8 mm ring to the graft with eight microsutures. Subsequently, we attached the graft including the ring end to the side of the recipient artery, also using eight microsutures. Then, the anastomosis was lased open, using the ELANA catheter 2.0 (Elana b.v.^®, Utrecht, the Netherlands) and a full thickness piece of recipient artery wall (the flap) was retrieved at the suction portion of the catheter (Fig. 1b). We put an aneurysm clip on the vein graft and checked the anastomosis for patency and leakage.

To make a SELANA anastomosis, a newly designed SELANA ring was used (Fig. 2a). This ring was equipped with two pins. The SELANA ring was first mounted on the end of a thin-walled polytetrafluoroethylene (ePTFE) graft with a diameter of 3 mm (W. L. Gore & Associates Inc, Flagstaff, AZ, USA) by our technician in the University Medical Center, Utrecht, The Netherlands (Fig. 2b). The SELANA was then mounted on the tip of a specially designed SELANA applicator (Fig. 2c, d). The SELANA was slid on to the recipient artery wall using the special form of the two pins (Fig. 3). First, the longitudinal parts of the two pins were simultaneously inserted in the vessel wall. When the resistance of the circumferential part of the pins was felt, the pins were aimed inside out again. Then the ring was gently pushed further in this direction, and the vessel wall ‘clicked’ over the circumferential part of the pins. In this way, only the circumferential part of each pin was exposed in the lumen of the artery (Fig. 3). The longitudinal parts of the pins were situated extraluminally on the arterial wall. Until this point, conversion was possible because the SELANA device can be removed again from the artery by pulling the device backward while holding the artery. This does not result in recipient vessel wall rupture, and the eventual leakage from the four perforation points is self-limiting. Subsequently, the anastomosis was sealed by a circumferential layer of Bioglue ® (Cryolife® Inc., Kennesaw, GA, USA) surrounding the ring on the abluminal part. The anastomosis was lased open with the ELANA 2.0 ® catheter, identically to the conventional ELANA anastomosis (Fig. 1b).

We made, in each of the four cadaver heads, seven anastomoses on the main proximal cerebral arteries of the left hemisphere and seven anastomoses on the main proximal cerebral arteries of the right hemisphere. The anastomoses were sequentially constructed on: (1) the P1/BA tip, (2) the P2, (3) the ICA before its bifurcation, (4) the ICA bifurcation, (5) the A1, (6) the proximal M1, and (7) one of the M2 arteries. In two cadaver heads, ELANA anastomoses were created in the left hemisphere and SELANA anastomoses in the right hemisphere (Fig. 4). In the two other cadavers, the side of the anastomoses was reversed (Fig. 5). Attachment time intervals were measured from the first penetration of the recipient artery in the cadaver (by either microsuture or anastomosis device) until the anastomosis was ready for lasing. The lasing procedure with the ELANA catheter was excluded from the time interval because it was the same in every anastomosis. This procedure consisted of introduction of the catheter in the bypass graft, 2 min of vacuum suction, two laser episodes (10 mJ, 40 Hz) of 5 s, retraction of the catheter from the anastomosis and applying a clip over the bypass graft. After every anastomosis, the surrounding brain, all exposed cerebral arteries, and all exposed cranial nerves (CN) were systematically inspected and scored for damage (yes-no) by an observer, other than the surgeon. If damage was observed, the video recordings were analyzed by two observers to find the exact cause of damage.

To compare application time intervals between ELANA and SELANA, we used non-paired t tests because in both groups, application time was normally distributed (Kolgomorov-Smirnov test, P value > 0.05). SPSS version 15.0 was used. Numbers are stated ± standard deviation unless otherwise indicated.